PROJECT SUMMARY Water and air pollutions are two sources of environmental exposures that lead to significant mortality and morbidity across the world. Due to poorer infrastructure, inadequate regulatory enforcement and awareness, the health burden of water and air pollution is disproportionately greater in developing countries, especially in South Asia. This proposal addresses primarily these two environmental problems through targeted maintenance and enrichment of our long-standing environmental epidemiology cohort ?Health Effects of Arsenic Longitudinal Study (HEALS)? which was initiated by Dr. Ahsan and his Bangladesh and US colleagues in 2000. Thus far, the cohort has been mainly addressing research questions on the health effects of arsenic exposure from drinking water. By maintaining the cohort infrastructure with longer follow-up and ascertainment of new health outcomes, we will substantially enhance our ability to evaluate health effects of arsenic exposure. In addition, by extending our exposure assessment scheme to add a comprehensive assessment of novel air pollution monitoring, coupled with targeted biosample acquisition and outcome ascertainment, we will open new opportunities (to researchers at large) for efficient investigation of health effects of air pollution by taking advantage of our unique cohort infrastructure. Specifically, we propose to: i) refine our cohort maintenance activities by ascertaining air-pollution related health outcomes through targeted enrichment of clinical outcome assessment infrastructure; ii) augment the exposure characterization of the cohort by instituting air pollution exposure assessment infrastructure; and iii) enrich our biorepository by initiating saliva sample collection for future investigation of the oral microbiome in relation to environmental health effects. The HEALS resource has already been successfully used by a wide cadre of researchers investigating the health effects of As, dietary and lifestyle exposures and, if funded, the proposed enrichment and maintenance activities will open new doors for efficient investigation of the health effects of air pollution, the underlying biology, and prevention avenues.